Linux distribution

A Linux distribution is a member of the family of Unix-like operating systems built on top of the Linux kernel. Such distributions (often called distros for short) are operating systems including a large collection of software applications such as word processors, spreadsheets, media players, and database applications. These operating systems consist of the Linux kernel and, usually, a set of libraries and utilities from the GNU Project, with graphics support from the X Window System. Distributions optimized for size may not contain X and tend to use more compact alternatives to the GNU utilities, such as BusyBox, uClibc, or dietlibc. There are currently over six hundred Linux distributions. Over three hundred of those are in active development, constantly being revised and improved.

Because most of the kernel and supporting packages are free and open source software, Linux distributions have taken a wide variety of forms—from fully featured desktop, server, laptop, netbook, mobile phone, and tablet operating systems as well as minimal environments (typically for use in embedded systems or for booting from a floppy disk). Aside from certain custom software (such as installers and configuration tools), a distribution is most simply described as a particular assortment of applications installed on top of a set of libraries married with a version of the kernel, such that its "out-of-the-box" capabilities meet most of the needs of its particular end-user base.

One can distinguish between commercially-backed distributions, such as Fedora (Red Hat), openSUSE (Novell), Ubuntu (Canonical Ltd.), and Mandriva Linux (Mandriva), and entirely community-driven distributions, such as Debian and Gentoo.

Kali, a Debian-based distribution with a collection of security and forensics tools,

Slackware, an old still pretty popular independent distribution from 1993

SystemRescueCd, a Gentoo-based distro for system rescue (voilá!)

Linux From Scratch, LSF, not a distro but a large document: if you want to learn the full installation process of a Linux by hand, this is the document for you. It will take weeks to accomplish, but after that, you're a Linux expert.